Air-cooled spark plug



July 16, 1929.

c. E. LEONARD AIR COOLED SPRK PLUG Filed July 28 1926 Patented yJuly 16, 1929.

UNITED STATES CALEB E. LEONARD, OF MIAMI, FLORIDA..

AIR-coornn sPARK PLUG.

Application filed July 28,

This invention relates to spark plugs for internal combustion engines, and aims to improve the construction and durability of such plugs by providing simple and efficient means for cooling the central electrode throughout part of its length within the insulating member.

An aim of the invention is to provide a plug in which the metallic plug body is entirely free from holes or apertures that might weaken the body or permit access of water to the interior of the body. In accordance with the present invention the cooling passages are formed entirely in the insulator, providing ample cooling capacity without in any way complicating the manufacture, assembly, or operation of the plugs. l

While I have illustrated preferred embodiments of my invention for purposes of illustration, it should be understood that vari-ous changes may be made in the structure without departing from the spirit and scope of the invention as hereinafter set foi'th and claimed.

In the drawings;

Fig. 1 is an elevation of a plug embodying the invention;

Fig. 2 is a section on line 2-2 of Fig. 1 ;l

Fig. 3 is a section through a modified form;

Fig. 4 is a section through a second modification;

Fig. 5 is a section on line 5-5 of Fig. 1;

Fig. 6 is a section on line 6 6 of Fig. 4.

Referring to the drawings more specifically, the plug comprises the insulating member 1() secured within the metallic body 11 by a flange nut 12. A central passage 13 extends through the insulator 10, the upper part of the passage being enlarged to form a shoullder 14. A central electrode 15 lits snugly into the passage 13 and carries a collar 16 engaging the shoulder 14. The central electrode is secured in place in any well-known manner with its upper end cooperating with the cap member 17.

The enlarged upper part of the passage 13 forms a chamber surrounding the electrode 15 within the insulator and the present invention concerns means for circulating air through this chamber. In the species of Figs. 1 and 2' a groove 18 is formed around the insulator 1926. Serial N0. 125,340.

just above the nut 12 and a passage 19 extends from the groove downwardly toward the bot tom of the chamber. A radial passage 20 is formed through the upper wall of the insulator. As the hot air rises it passes out the opening 2O and draws cool air through the opening 19 and int-o the lower part of the chamber.

The groove 18 forms a convenient point of attack for the drill in forming the passage 19, and the groove also increases the dielectric properties of the insulator, since it has been Y found that any break in the surface of the insulator reduces the likelihood of the current arcing from the cap 17 to the nut 12.

In the species of Fig. 3 the rib 21 forms a point of departure for drilling the passage 19. A second passage 22 extends from the chamber within the plug to the annular space between the insulator and the plug body. This second passage provides means for the escape of the air from the annular space as the plug becomes heated in service.

In the modification of Fig. 4 a longitudinal channel 23 is formed in the outer surface of the insulator and extending within the plug body. A radial opening 24 admits air from ltOhe channel to the bottom of the central chamf It will be clear that in each of the forms disclosed the cooling passages are formed entirely within the upper part of insulating member, leaving the shell free from apertures and the parts adjacent the assembly joints strong and rigid.

I claim:

A spark plug comprising a body, a core located in the body and having a portion of vits peripheral surface spaced from the inner surface of the body, said core having an interiorly located chamber, an electrode passing through the core and having at points between its ends an outstanding flange bearing against the lower wall of the chamber and holding the exterior surface of the electrode spaced from the wall of the chamber, said plug having an outlet passageway passing through its side and communicating with the upper portion of the chamber, said plug having at the intermediate portion of its side inwardly converging passageways which face of the core and the interior surface of the merge at their inner ends with each other body and the outer end of the other second and which communicate with the interior of mentioned passageway being disposed above 10 the chamber at a. point common to both of the the upper end of the body.

last mentioned passageways7 the outer end of In testimony whereof I aliX my signature. one of the last mentioned passageways being disposed in the space between the exterior sur- CALEB E. LEONARD. 

